I think the biggest difference isn't just the frame, but the attitude. In the ballroom world, the dance is more upright, the posture is "tall", and the attitude is very much more about precision. In the non-ballroom (nightclub or street) swing, EC still should have frame, but the anchor is down more so. The posture has bent knees, and and the shoulders should be more even. I think in recent years EC has become more codified, and my own person teaching style is based on the posture and frame of smooth-style Lindy.

Looking at the syllabus video for the "throwout" in EC swing, I can tell you that the non-ballroom version would not have the lady facing away from the man at any point in that move. The quick reason for that is responsiveness: as EC moves to faster tempos, turning away from the lead delays reaction time, and you can't follow as easily into the next move with effortlessness and ease. When I teach, this is a correction I make right away. Once in a while, I will have a student that learned in a ballroom heavy studio, and they will fight me on this point up until I move the tempo over 120 beats per minute.

Also, non-ballroom EC leaves much of the presentation up to the dancer. Once you teach the basic 10 or so moves (I only teach single and double time for a total of 15 minutes combined in a 6 hour series, the rest is all triple-step) I really work with my students to express their personality in the dance. Yes, in the end, their style will resemble that of their primary instructor, but I aim to make my influence more of a nuance in favor of their own style. I prefer that my students don't look like cookie-cutters of me or each other.